This study reports the effects of fuelling a heavy-duty single-cylinder research
engine with pilot-ignited late-cycle direct-injected natural gas diluted with 0, 20, and 40 per
cent nitrogen. The combustion duration is unaffected while its intensity is reduced and its
stability is increased. Emissions of nitrogen oxides, particulate matter, hydrocarbons, and
carbon monoxide are all reduced, with no effect on the engine’s performance and efficiency.
The results indicate the benefits of increased in-cylinder turbulence and are of particular
relevance when considering fuel composition variations with non-conventional sources of
gaseous fuels.